1. Field of the Invention
This invention relates generally to a radio control system, and more specifically to a radio control system having a transmitter and a radio-controlled model toy on which a d-c power supply, a receiver and two motors are mounted, wherein a control pulse signal having a signal "1" level and a signal "0" level is transmitted from the transmitter, and the duration of the signal "1" or "0" level is increased or decreased so that the travelling direction, for example, of the model toy can be changed.
2. Description of the Prior Art
One of well-known radio control systems for maneuvering electric model airplanes, etc. is the digital proportional system, in which a plurality of servo-mechanisms are controlled by signals one cycle of which consists of a variable with control pulses corresponding to each servo-mechanism and a timing pulse. However, radio control systems based on the digital proportional system are generally too expensive to incorporate in model cars and other relatively simple model toys in which radio control is used only for changing the travelling direction.
In this type of radio-controlled model toys such as model cars, a radio control system having a receiver provided with two resonance circuits with slightly different resonance frequencies, and a transmitter capable of shifting the transmitting frequency either in positive or negative direction has been used. This system has such a construction that two motors are used to separately drive right and left wheels so that the travelling direction can be changed based on the difference in the output levels of the two resonance circuits in the receiver caused by shifting the transmitting frequency in the transmitter. However, there is a limit in miniaturizing resonance circuits because the resonance frequencies of the resonance circuits are usually in the low frequency band. This makes it difficult to apply such a radio control system to the design of small-sized model toys, such as model cars of approximately 5.times.10.times.5 cm in size.